Error from `min_version` should be prioritized

[mfansler]

Is your feature request related to a problem? Please describe. Ideally, the snakemake.utils.min_version function checks for a minimum version and raises a WorkflowError when that is not satisfied. However, in practice it often fails to provide value. For example, the use of min_version("6.0") to ensure support for module declarations never yields a WorkflowError when using versions below v6.0, but instead ends with SyntaxError. This undermines using it.

I have not dug into the code, but the behavior would suggest that a first pass of parsing occurred (at least in pre-6.0 versions) prior to any code evaluation.

Describe the solution you'd like Ensure that a min_version call appearing anywhere in a Snakefile is evaluated with priority so that version issues propagate to the user rather than syntax errors. Perhaps if the regular parsing fails, it could be caught before propagating and a rudimentary check for min_version calls could be made and reported.

Describe alternatives you've considered I declare in documentation minimum Snakemake versions. Possibly it should be documented that min_version, even at the top of a Snakefile, does not guarantee a WorkflowError.

Additional context I realize the criticism here is about behavior of older versions and I don't expect any retroactive patching. However, I couldn't find previous threads that raised this particular point so that it could be addressed in versions moving forward.

---

Minimal example

Snakefile

from snakemake.utils import min_version
min_version("6.0")

rule all:
    input: "b.txt"

module a_factory:
    snakefile: "a_factory.smk"

use rule * from a_factory

rule b_from_a:
    input: "a.txt"
    output: "b.txt"
    shell: "echo 'found {input}' > {output}"

a_factory.smk

rule make_a:
    output: "a.txt"
    shell: "echo 'Made in A Factory' > {output}"

Result in Snakemake v5.29

$ snakemake -np
SyntaxError in line 7 of /Users/mfansler/scratch/smk-version-fail/Snakefile:
invalid syntax

[MarwanMabrouk]

But it seems this behavior doesn't happen in the latest releases

[mfansler]

But it seems this behavior doesn't happen in the latest releases

Do you have an example? That is, a Snakefile that uses a syntactic feature requiring a minimum, and running a Snakemake below that minimum leads to the minimum violation being detected instead of a syntax error.

[MarwanMabrouk]

But it seems this behavior doesn't happen in the latest releases

Do you have an example? That is, a Snakefile that uses a syntactic feature requiring a minimum, and running a Snakemake below that minimum leads to the minimum violation being detected instead of a syntax error.

I did a quick test in snakemake version 8.4.3 with the same minimal example you provided and I only changed min_version("6.0") to min_version("9.0")

and I got the following result

$ snakemake -np
WorkflowError:
Expecting Snakemake version 9.0 or higher (you are currently using 8.4.3).

[mfansler]

@MarwanMabrouk that test does not satisfy the specifications. Perhaps I should clarify that when I said "that uses a syntactic feature requiring a minimum" I intended it as requiring the specific minimum. A relevant test should be using some new syntax that was introduced in the minimum version (i.e., v9.0 in this case).